Correlation between the amplitude of action potentials and the rate of conduction along axons of the output cells of the sensomotor cortex

Antidromic responses of neighbouring neurones in micro-areas of the sensorimotor cortex to the stimulation of fibers of the pyramidal tract as well as of the red nucleus and thalamic nuclei VPL and MGB, were studied in acute experiments on unanesthetized immobilized cats. Depending on the velocity of conduction along the axon, the neurones of all the categories were divided into fast and slow cells. When examining the two neuronal groups most differing in AP amplitude (N1 and N3), it was found that N1 neurones were mainly fast-conducting and N3 neurones-- slow-conducting. The conclusion is made that at multineuronal recording, each of the examined categories of the output neurones is characterized by positive correlation between AP amplitude and the axon conduction velocity and consequently, the size of the cell.